feat: auto-preview, timestamped/grouped output, folder memory; fix batch format

- Auto-preview the first image after a folder loads (both panels), so the
  canvas isn't empty (§17.8).
- Group exports as <output_dir>/<timestamp>/<print_stem>/<garment_stem>.<ext>;
  one timestamp per export run, shared across the batch (§17.9).
- Remember the last garment/print folders and reopen the picker there;
  persisted via config, wired through main_window (§17.10).
- Shrink the 3 box templates further and lower them (chest placement).
- Fix: batch export ignored the chosen format/quality/output dir because the
  queue never received ExportOptions. Export panel now emits
  export_options_changed → queue.set_export_options (+ initial sync) (§17.11).

Docs: PRD 6.1/6.8/9, architecture 4.12, UI design 5.1, tasks.md 17.8–17.11.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/services/file_service.py

@@ -1,5 +1,6 @@
 import logging
 import sys
+from datetime import datetime
 from pathlib import Path
 from typing import List
 
@@ -102,20 +103,32 @@ def scan_image_folder(folder) -> List:
 # 安全输出文件名
 # ---------------------------------------------------------------------------
 
+def timestamped_run_dir(base_dir):
+    """Return base_dir/<YYYYmmdd_HHMMSS> for grouping one export run.
+
+    Compute this once per export run (a batch, or a single export) and pass the
+    result as the output_dir to make_safe_output_path, so repeated runs land in
+    separate timestamped folders instead of mixing together.
+    """
+    return Path(base_dir) / datetime.now().strftime("%Y%m%d_%H%M%S")
+
+
 def make_safe_output_path(output_dir, garment_path, print_path, output_format="PNG"):
     """Return an output Path that will not overwrite an existing file.
 
-    Filename pattern : <garment_stem>_<print_stem>.<ext>
+    Outputs are grouped by print into a subfolder named after the print file:
+        <output_dir>/<print_stem>/<garment_stem>.<ext>
     If that path exists, appends _1, _2, ... until a free slot is found.
+    (The composer creates the subfolder when saving.)
     """
-    output_dir = Path(output_dir)
     ext = ".png" if output_format.upper() == "PNG" else ".jpg"
-    stem = "{}_{}".format(Path(garment_path).stem, Path(print_path).stem)
+    target_dir = Path(output_dir) / Path(print_path).stem
+    stem = Path(garment_path).stem
 
-    candidate = output_dir / (stem + ext)
+    candidate = target_dir / (stem + ext)
     counter = 1
     while candidate.exists():
-        candidate = output_dir / ("{}_{}{}".format(stem, counter, ext))
+        candidate = target_dir / ("{}_{}{}".format(stem, counter, ext))
         counter += 1
 
     return candidate

src/services/template_service.py

@@ -15,25 +15,25 @@ _TEMPLATES_FILENAME = "templates.json"
 BUILTIN_TEMPLATES: List[Template] = [
     Template(
         name="正方形模板",
-        x_ratio=0.34, y_ratio=0.22,
-        width_ratio=0.32, height_ratio=0.32,
+        x_ratio=0.40, y_ratio=0.40,
+        width_ratio=0.25, height_ratio=0.25,
         rotation=0.0, type="builtin",
     ),
     Template(
         name="纵向长方形模板",
-        x_ratio=0.35, y_ratio=0.16,
-        width_ratio=0.30, height_ratio=0.46,
+        x_ratio=0.435, y_ratio=0.385,
+        width_ratio=0.20, height_ratio=0.30,
         rotation=0.0, type="builtin",
     ),
     Template(
         name="横向长方形模板",
-        x_ratio=0.27, y_ratio=0.26,
-        width_ratio=0.46, height_ratio=0.30,
+        x_ratio=0.385, y_ratio=0.435,
+        width_ratio=0.30, height_ratio=0.20,
         rotation=0.0, type="builtin",
     ),
     Template(
         name="左胸小号模板",
-        x_ratio=0.50, y_ratio=0.22,
+        x_ratio=0.55, y_ratio=0.30,
         width_ratio=0.16, height_ratio=0.16,
         rotation=0.0, type="builtin",
     ),